1. Field of Invention
The present invention relates generally to a data converter and specifically to compensation of impairments present within the data converter.
2. Related Art
Data converters are frequently used in mixed-signal electronic systems. Mixed signal electronic systems include both analog signal environments and digital signal environments. The analog signal environments primarily operate upon analog signals while the digital signal environments primarily operate upon digital signals. A mechanism is required to transport signals from one environment, such as the analog signal environment, to another environment, such as the digital signal environment. Commonly, an analog-to-digital converter (ADC) is used to convert analog signals from the analog signal environment to digital signals for the digital signal environment. Similarly, a digital-to-analog converter (DAC) is used to convert digital signals from the digital signal environment to analog signals for the analog, signal environment. The ADC and the DAC are commonly referred to as data converters.
Advances in integrated circuit (IC) technology have generally made it advantageous to shift more of the signal processing burden to digital circuits, and therefore there is a continuing requirement for data converters with better performance. Data converters are typically characterized primarily by two measures: sampling rate and effective-number-of-bits (ENOB). The sampling rate for the ADC represents a rate at which an input analog signal is sampled and quantized into a digital signal. For an ADC, ENOB is a measure of how accurately the input analog signal is converted into digital form. It is a combined measure that includes quantization noise, thermal noise, distortion, sampling jitter and other imperfections.
The sampling rate for the DAC represents a rate at which input digital data samples are converted into an analog output voltage or current. For a DAC, ENOB is a measure of how accurately the input digital samples are converted into analog form. It similarly is a combined measure including all imperfections. There may be differences in the application-specific definition of ENOB based on the relative importance of different imperfections in a given system. Often, the signal-to-noise (SNR) and signal-to-distortion (SDR) ratios are given in addition to ENOB.
In addition to these performance measures, it is desirable for data converters to dissipate as little DC power as possible and to cost as little as possible. These are universal goals in all electronic systems. In the mixed-signal electronic systems, low cost is related to low die area. In other words, it is desirable that the data converter design have as small an area footprint as possible within a die that forms the mixed-signal electronic system.
Conventional approaches to data converter design have emphasized analog techniques to obtain high sample rate and high ENOB. Often, these analog techniques will require high power dissipation. In general, analog circuits with high dynamic range (low noise and low distortion) require large power dissipation. High ENOB converters often require precise component matching to obtain high resolution (low quantization noise). Matching of components (transistors, resistors and capacitors) in an IC usually implies large die area. Large components match better than small ones since random fluctuations are averaged spatially.
Thus, there is a need for a data converter that leverages digital signal processing techniques to correct analog imperfections and relaxes stringent analog specifications that lead to high power dissipation and high cost that overcomes the shortcomings described above. Further aspects and advantages of the present invention will become apparent from the detailed description that follows.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.